How do you know when to close a profile?

We rely on help from you. In every profile there is a "Report Member" link. Use this link to report "bad" members to us.
If the evidence is clear, or when a member gets a certain number of complaints, his or her profile will be closed.

All this talk about closing profiles gives me the creeps. Can my profile be closed too?

Relax... if you play by the rules there is no risk of your profile being closed at all.
Just be nice to the world, and the world will be nice to you. It's really as simple as that.